Conventionally, a drip irrigation method is known as a method for culturing plants. In the drip irrigation method, a drip irrigation tube is disposed on the soil where plants are planted, and irrigation liquid such as water and liquid fertilizer is dropped from the drip irrigation tube to the soil. The drip irrigation method has been increasingly attracting attention in recent years since the method can minimize the consumption rate of the irrigation liquid.
Normally, the drip irrigation tube includes a tube in which a plurality of through holes for discharging irrigation liquid are formed, and a plurality of emitters (also called “drippers”) for discharging irrigation liquid from respective through holes. In addition, as the emitter, emitters which are joined on the inner wall surface of the tube (see, for example, PTL 1), and emitters which are inserted to the tube from the exterior of the tube are known.
PTL 1 discloses an emitter configured to be joined on the inner wall surface of a tube. The emitter disclosed in PTL 1 includes a first member including a water intake port for intake of irrigation liquid, a second member including an outlet for discharging the irrigation liquid, and a film member disposed between the first member and the second member. On the inside of the first member, a valve seat part disposed to surround the water intake port and a pressure reducing groove that serves as a part of a pressure reduction channel are formed. In the film member, a through hole is formed at a position corresponding to the downstream end of the pressure reducing groove.
When the first member, the film member and the second member are stacked, the pressure reduction channel is formed, and the film member makes contact with the valve seat part to close the water intake port. In addition, a channel for carrying the irrigation liquid from the water intake port to the outlet is formed.
In the emitter disclosed in PTL 1, when the pressure of the irrigation liquid in the tube is equal to or greater than a predetermined pressure, the film member closing the water intake port is pushed by the irrigation liquid, and the irrigation liquid flows into the emitter. The pressure of the irrigation liquid proceeded into the emitter is reduced by the reduction channel, and the irrigation liquid is quantitatively discharged from the outlet.